ZenFone 5 model number A500CG/A501CG and ZenFone 6 model number A600CG/A601CG are all ready for a OTA upgrade to Lollipop, Asus has started the rollout of firmware build WW_V188.8.131.52 to all the above mentioned models, while the ZenFone 4 model number A400CG/A400CXG should see an upgrade OTA to firmware build WW_V7.3.3, all delivering Lollipop to Asus Zenfone handsets.
ZenFone 5 and 6 owners can also download the firmware straight from Asus’ website, that if they don’t want to wait for a OTA download notification and have the know-how to install a ROM manually.
Download ZenFone 6 firmware
Download ZenFone 5 firmware
For the change log / release notes for each device, please check source links below.